Abstract
At present, chemical Si/Al sources are mainly used as precursor materials for the manufacturing of zeolites. Such precursor materials are quite expensive for commercial synthesis. Here, we have reported the synthesis of Ca-based zeolite from incense stick ash waste by the alkali-treatment method for the first time. Incense stick ash (ISA) was used as a precursor material for the synthesis of low Si zeolites by the alkali-treatment method. The as-synthesized zeolites were characterized by various instruments like particle size analyzer (PSA), Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), electron diffraction spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray fluorescence (XRF). FTIR and XRD helped in the identification of the microstructure and crystalline nature of the zeolites and also confirmed the synthesis of Ca-based zeolite with two thetas at 25.7°. The microscopic analysis by FESEM and TEM exhibited that the size of synthesized Ca-rich zeolites varies from 200 to 700 nm and they are aggregated and cuboidal in shape. Additionally, structural, electronic, and density of states’ characteristics of gismondine (Ca2Al4Si4O16·9H2O) structures were evaluated by computational simulations (first principle, density functional theorem). The structural optimization of structures was carried out in the first stage under the lowest condition of total energy and forces acting on atoms for the lattice constant, as well as the available experimental and theoretical findings. The present research approach predicted the transformation of ISA waste into a value-added mineral, i.e., zeolite, which was further used for the removal of both heavy metals and alkali metals from fly ash-based wastewater using inductively coupled plasma-optical emission spectroscopy (ICP-OES).
Highlights
Zeolites are crystalline aluminosilicates having elements either from group I or II as counter ions [1]
Through alkali activation and simultaneous heating, the silica phase (15-20%) existing in Incense stick ash (ISA) participates in the zeolitization process by dissolving into the solution whereas quartz or mullite remains in the nonreactive mineral phase [46]
The picture clearly shows that s, p, and d are the most contributed energy in the formation of gismondine type zeolite; the Ca and Al d orbital is the strong peak at Fermi level just above the conduction band maxima (CBM) in the range 0 to -8 eV, as well as some density contribution near the valence band minima (VBM) in the region 4 eV to 18 eV
Summary
Zeolites are crystalline aluminosilicates having elements either from group I or II as counter ions [1]. Porous nature, negative charge, water-insoluble, higher melting point, and water trapping property [12,13,14] make them a potential material as an adsorbent [15] for wastewater treatment [16], as fertilizers in agriculture [17], and as an ion exchanger [18,19,20,21,22,23,24,25,26] Based on their origin, zeolites can be of two types, i.e., natural or synthetic [27, 28]. The utilization of ISA for zeolites will reduce the disposal problem of ISA and water pollution
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